User-written components
Consider deploying user-written components to define custom behavior as part of your solution.
Server-related components
All of these components must be created as Java™ classes and put on the classpath of the Diffusion™ server.
- Authentication handlers
- These components handle authentication of clients that connect to the Diffusion server or change the principal that they use to
connect to the Diffusion server. If the client connection is
allowed, the authentication handler assigns roles to the client session.
You can have zero, one, or many authentication handlers configured on your Diffusion server.
For more information, see Developing a local authentication handler and Developing a composite authentication handler.
Note: Local authentication handlers, on the Diffusion server, can be written only in Java. However, control authentication handlers that are part of a client whose API supports Authentication Control can be written in other languages. - Hooks
- Startup and shutdown hooks are called by the Diffusion server.
The startup hook is instantiated and called as the Diffusion server starts and before publishers are loaded.
The shutdown hook is called as the Diffusion server stops.
For example, you can use a shutdown hook to persist some aspect of the state of the Diffusion server to disk.
- HTTP service handlers
- These components handle HTTP requests as part of an HTTP service in the Diffusion server's built-in web server. Provide a user-written HTTP service handler to enable the Diffusion web server to handle any kind of HTTP request.
- Thread pool handlers
- These handlers define custom behavior in the Diffusion server
related to the inbound thread pool.
You can provide a rejection handler that customizes the behavior when a task cannot be run by the thread pool. By default, if a task cannot be run by the inbound thread pool — for example, if the thread pool is overloaded — the calling thread blocks until there is space on the queue.
You can provide a notification handler that receives notifications when events occur on the inbound thread pool.
Topic- and data-related components
All of these components must be created as Java classes and put on the classpath of the Diffusion server.
- Message matchers
- Message matchers are used to customize conflation behavior. These classes
that define how the Diffusion server locates messages on a
client's message queue that are to be conflated.
By default, messages for conflation are matched if they are on the same topic.
For more information, see Conflation.
- Message mergers
- Message mergers are used to customize conflation behavior. These classes
that define how the Diffusion server conflates matching
messages.
By default, the older of the matching messages is removed.
For more information, see Conflation.
- Routing topic handlers
- These components handle the behavior of a routing topic. When you create a
routing topic, you provide a routing topic handler that, when a subscription
to the routing topic is made, maps the routing topic to another topic on the Diffusion server on a client-by-client basis.
For more information, see Routing topics.